The first computer graphic system to do 3D keyframe based human joint animation was a pure kinematic system introduced by [STERN, G., 1978. Garlands animation system (gas) a system for computer-aided keyframe animation. Doctoral Thesis, incorporated by reference herein], in which hand-made static poses were interpolated by smooth splines. Since then, there has been much work on automating the computer simulation of 3D walking characters. This work has variously focused on kinematics and dynamics.
The first high level parameterized kinematic based automation of walking was done by [ZELTZER, D., 1982. Motor Control Techniques for Figure Animation. IEEE Computer Graphics and Applications, 2(9):53-59, incorporated by reference herein]. Hierarchical concurrent state machines were used to control the gait of a synthetic skeleton. A pre-defined key posture was associated with each FSM state. Transitions between states produced linear interpolations between key-postures, producing joint angles that drove the animation.
Bruderlin and Calvert [BRUDERLIN, A., and CALVERT, T., 1989. Goal-directed, dynamic animation of human walking, In Computer Graphics (Proceedings of ACM SIGGRAPH 89), 23, 4, ACM, incorporated by reference herein] achieved non-slip foot placement by making the contact foot the root of the kinematic chain, and treating it as an inverted pendulum. They later combined this approach with parameterizable styles of walking [BRUDERLIN, A., and CALVERT, T., 1993. Interactive Animation of Personalized Human Locomotion. In Proc. of Graphics Interface 93, pages 17-23, incorporated by reference herein].
Boulic [BOULIC R., MAGNETAT-THALMANN, N., and MAGNETAT-THALMANN, D., 1990. A global human walking model with real-time kinematic personification. Visual Computer, 6(6):344-358, incorporated by reference herein] used forward kinematics followed by an inverse kinematics post-processing step to modify foot position when feet penetrated the ground, and then later modified this approach to maintain proper balance centering of the body over the feet [BOULIC, R., MAS, R., and MAGNETAT-THALMANN, D., 1996. A robust approach for the center of mass position control with inverse kinetics. Journal of Computer and Graphics, 20(5), incorporated by reference herein].
Ko and Badler [KO, H. and BADLER, N., 1996. Animating Human Locomotion in Real-time using Inverse Dynamics, Balance and Comfort Control. IEEE Computer Graphics and Applications, 16(2) :50-59, incorporated by reference herein] did post-processing inverse dynamics on kinematic walking, adjusting the results of forward kinematics to ensure that movement embodied appropriate forces. Spacetime constraints on the body center were introduced by Witkin [WITKIN, A. and KASS, M., 1988. In Computer Graphics (Proceedings of ACM SIGGRAPH 88), 22, 4, ACM, incorporated by reference herein] to compute these correcting dynamics, specified as the minimization of a cost function, over the entire course of an animation, rather than sequentially in time. Cohen [COHEN, M., 1992. Interactive spacetime control for animation. In Computer Graphics (Proceedings of ACM SIGGPAPH 92), 26, 4, ACM, 293-302, incorporated by reference herein] refined this approach to allow space-time windows to be specified, so that these dynamic adjustments could be applied interactively. Gleicher [GLEICHER, M., 1997. Motion editing with spacetime constraints. In Proc. of Symposium on Interactive 3D Graphics, incorporated by reference herein] extended space-time constraints to the handling of constraints on all kinematic trajectories of the walking figure.